Means for operating alternating-current machines in parallel.



No. 876,686. PATENTED JAN. 14, 1908.

M. BROOKS & M. K. AKERS.

MEANS FOR OPERATING ALTERNATING CURRENT MACHINES IN PARALLEL APPLIOATION' FIT-ED JAN, 18. 1907.

.Dl a/ IIIIIIIIIIII r\ rfl ATTO Y MORGAN BRooKs AND MILTON KENT AKERS, or URBANA, rL'L No Is. l ilf/IEANS'FOR ornzanrrne AL'fERNATING-GURRENT M AoirniEs IN r'anaptn n 5 'ful Improvements in Means for Operating AlternatingCurr'ent Machines in Parallel, of

which-thefol-lowingis a specification.

Our invention relates tothe operation of any kind and type of alternating current machines. 1 I lEor the sake of1simplicity of description,

we'will ex'plain'the in'vention as applied to single phase alternating current generators.

Theseveral objects of the invention are to obtain approximately and automatically any desired distribution of load. currents among a plurality of coupled alternating current machines,.witho'ut the employment .of cen- "trifu'gal' and other mechanisms; to rovide for self synchronizing such machines oth on coupling and duringoperation While coupled to. permit the transfer of surplus energy from- "a machine'of high excitation to a machine of low excitation automatically, thereby im proving the power factor of the system, and correspondingly increasing the capacity for the load current; to diminish hunting and racing; 'to elim'na'te difii'cultie's from differ ences of wave form; to be able to'include and. hexclude from the circuit one or more ma chines, and cause tho'sein use to properly and automatically divide the load among themselves; and to operate successfullymachines at different distantstationsin parallel With proper dividing of theload currents au tomatically.

Other minor results will appear from the following explanations.

Without regard'to the scopes of invention 7 which are attended to in the clalms, theorganization comprising ourlnvention consists] primarily of alternating current machines,

and inductive'me'ans, for compelling a division of loadeurrentsflamong the several machines automatically, and. secondarily, of self-synchrtihizing coils in circuit with said machines. 5o

Other'detailsw ill a pear hereinafter We will now desc'ri e specifically, exactly what the-drawing shows, and howthee-lements exhibited therein operate;

Thesingle figure of drawing is a diagraml of the electric circuits and apparatus; 4

, Specification of Illlettersv Patent.

- Applicatioirfileddlanuary 18.1907, ,seanro'. 352.923,

sizes as indicated, our invention-being circuit with each other.

7 each machine, orgroup of machlne s change in'the'other generators, is 0 .tion of load currents.

-1, 2, 3, 4;, 5, are alternat ng current gen;

. Patented Jen.

erators connected ,to parallel circuits. vThey may be of 'plicable to like. or, dissimilar"al-ternatin 0 rent machines. v i D D D D are transformers, 1W

spective primary coils are P P111, ;P' i

a group the 5 the first'of which is in series circuit with composed of the generators l and.--2 ,and others of which are in series circuit with remaining generators 3, 4, and 5 singly; The secondary coils S S}, 8*, S, of above named transformers are, ofa given phase, and rare in a normally closed. series a; fit-" d 2 are switches for'short-circuiting the'said-sec ondary coils individually. 'We will'now set'forth theoperation ofi'the system as far as the use of the transformersis concerned. They are designed to cart ,in their. primarv circuits, currents prferab y direct proportion to the full load-cu oasemay be, and 1n-their"secondary}c I, m a. single-current alike in all" transforme hen proportional currents "are naturally,

flowing through/each .machine,- the 'tr formers, Di, D D3, D; are non-ma e since in their primary coilsfl PEP, I, P 1

the proportional currents for which th designedjand the seconda coils? 7 S being,all' designed for t iels are not p'nly connected in a direction, but are-in a closed on these circumstances, practically motive force existsat the terin'i said transformers. 'Any change rent fromajsingle machine, as for ex "the generator 3,; Without a .corr' the reaction of the-primary coil of ts former, D If, however, the current I this last'named primaryIcoil does.'chai f causes, through the connected 'seco'iidarie I of the transformers, a'correspondingchange in' the ciirrent fronr all the other generators,

approximately restorin the "proper pro'porimil arly, any change of excitation or of. driving force, in one'gehr ful rlesult is the securing of an average-elec-g tro-motive' force and fan equalizatlon of power. The transformers, are therefore so connected as to be a proximately non-in 1"10 ductive so long as the desired division of load current exists, but. automatically inductive erator, thus affects all generators. The usewhenthe' proper division is disturbed, where by a satisfactory approximation of balance o the load current .1s restored. The non-inductive connection for balanced circuits is intended to apply s ecifically to the fundamental frequency 0 the current in an ap- Baratus, controlled, but willalso ap y to lgher harmonic frequencies,provided these higher harmonics are similar inthe several machines. Different higher harmonics, and

'harmonics in different phase relation to the for such unbalanced harmonics,

transformer is for 'acti "ries circuit with the gengrator 2. [generators -1 and 2, whi e the transformer D fundamental, producing that difference in wave form, which is often a source of trouble in operating, become opposed by the relatively highinductance of the, transformers and are checked thereby.

, D"? isanauto-transform'er, one portion of the coil 0f wh1ch 1s in series c'ircu1t with the generator -'1, while the other portion is inse- Said auton between the two is for'action between these two generators l and 12', on the one hand, considered as a "group of generators, and the other genera- .tors ndivrdually, on the other hand. By simply closing the shortcircuiting switches 1, 2, 3? and 4 the alternating current generators 3, 4', 5, and the group 1, 2, may-be placedin the ordinary parallel circuit connection without securin any balance ofthe load. The primary coils% ductive for any value 'of current whatever,

loss of the transf onners is also trivial, since there i's then no appreciable terminal voltage,

' By openin' the circuitclosers G G G, G

Whichisa measure of core losses.

- andGi, the a tern'a'ting current e'nerators 3, 4,;5", andLthe group composed o the generators 1 and2, may becut out of clrcult.

' The transformers may be cutout of circuit hyvtirpening the circuit closers 'g;

, g do not allege th t there is obtained a mathematical accuracy of control of. the curront-loads byour-invention,.but'suchis not necessary in practice. We secure a balancin'gi-ofthe currents conformable t6 the ri id requirements in large orsmall'plants. n theo eration of our system as above de-' scribed, t e alternating current generators circuit.

. 1 are 1111' thereby rendered completely non-in- 35 and their circuits have merely the almost .negligibleresistance'of the coils. ,The core unless connected together rig'i ly. To maintain them in step while indepe dently driven we provide reactance coils, E, Efl-Ei E and E preferably without iron cores, and connected in series with the respective machines and the extra or synchronizing bus bar Q and line bus bar B. The reactance coils also serve to synchronize the generators during the process of coupling the same in parallel I These coils should .be so designed as never to allow excessive current to flow be tween the generators 1, 2, 3, sand 5, even at opposition of phase, and yet to permit enough current to synchronize a generator to be connected, and to maintain it in synchronism. An impedance for these coils E E E E, and E which. will allow about half the full load current to flow on applying the full generator voltage, has been found satisfactory.

In normal 0 oration, the cross currents are confined to t ese self-synchronizing reactances,'since the impedance'of the balancing transformers is entirely too great to allow sufficient. cross currents to flow for maintaining synchronism under ordinary conditions. The current re uired in these synchronizing coils may be eterminle'd by an ammeter. Under favorable conditions, the synchronizing currents in these coils may be reduced to a negligible quantity-insuring the highest eiiiciency. I They should not be cut out of 'circuit after the machines are con led, for

they not only synchronize on coup ing, but during operation aftercoupling;

What we claim and desireto secure by Letters Patent, is,- r 'llhe combinatiorrof a plurality of alternating current machines connected in parallel circuit, electric transformers, primary coilsfor said transformers included in series circuit with the respective machines, and the secondary coils of a iven phase, for said transformers connected in a closed series circuit with one another, and self synchronizing reactance coils in-circuit with the respective machines.

MORGAN BROOKS. MILTON KENT AKERS. Witnesses: 7

J HN H. SAVAGE, 4 FRANK H. Boees. 

